The present invention relates to a transfer method for increasing or decreasing the transfer Velocity of a workpiece (including a material) when the workpiece moving on a transfer line is handed over to another transfer line, and a transfer apparatus having the accelerating/decelerating function.
Japanese Patent No. 2580493 discloses an apparatus for cutting sanitary goods, and increasing the transfer pitch of the cut sanitary goods. Specifically, the die cutter roll for cutting and transferring the sanitary goods hands over the sanitary goods to a transfer roll that rotates at a higher velocity than the circumferential velocity of the die cutter roll, whereby the transfer pitch of the sanitary goods on the transfer surface of the transfer roll is greater than the transfer pitch thereof on the transfer surface of the die cutter roll.
Japanese Laid-Open Patent Publication No. 63-317576 discloses a technique of cutting an elastic tape by a rotating drum, turning the cut elastic tape pieces on the rotating drum by 90xc2x0 with respect to the transfer direction, and attaching the elastic tape pieces to an adherend sheet being transferred by an adherend sheet transfer apparatus. The circumferential velocity of the rotating drum is higher than the circumferential velocity of an elongation roller for feeding the elastic tape to the rotating drum, and the elastic tape, which is a continuous member, is gradually elongated while being in contact with the surface of the rotating drum, thereby increasing the interval between the cut elastic tape pieces.
Japanese Laid-Open Patent Publication No. 57-102427 discloses a transfer apparatus for transferring an elongate stick-shaped item such as a cigarette in a direction perpendicular to the axial direction thereof. This transfer apparatus holds each stick-shaped item in a housing having a semicircular cross section, and changes the transfer pitch of the stick-shaped items held on a linking conveyer, which is disposed between two conveyers, while the linking conveyer moves about halfway around.
U.S. Pat. No. 5,025,910 discloses a technique for turning a vacuum pickup shoe by 90xc2x0.
However, when transferring a soft workpiece which has a length or width such as sanitary goods, for example, by using the conventional techniques described above, the workpiece is likely to be wrinkled when it is handed over between rotating members such as rolls and drums, thereby failing to sufficiently satisfy the requirement of transferring an item stably and at a high velocity. The present invention provides a transfer method and a transfer apparatus capable of satisfying such a requirement.
A transfer method of the present invention is a transfer method for transferring a workpiece from a preceding stage to a subsequent stage by using a transfer apparatus including at least one transfer section capable of revolving around a rotation axis, the method including: a pickup step, wherein in order for the transfer section to pick up the workpiece transferred by the preceding stage at a first transfer velocity, the transfer section moves at a pickup velocity substantially equal to the first transfer velocity in a pickup area having a width; a velocity-changing step of changing the transfer velocity of the transfer section while the transfer section is holding the workpiece which has been picked up; and a hand-over step, wherein in order to transfer the workpiece at a second transfer velocity by the subsequent stage, the transfer section moves at a hand-over velocity substantially equal to the second transfer velocity in a hand-over area having a width, wherein the pickup velocity and the hand-over velocity are different from each other.
A transfer apparatus of the present invention is a transfer apparatus, including at least one transfer section capable of revolving around a rotation axis, and a velocity-changing section for changing a transfer velocity of the transfer section, wherein: in order for the transfer section to pick up a workpiece transferred at a first transfer velocity, the transfer section holds the workpiece while moving at a pickup velocity substantially equal to the first transfer velocity in a pickup area having a width; the velocity-changing section changes the transfer velocity of the transfer section holding the workpiece; in order to transfer the workpiece at a second transfer velocity outside the transfer apparatus, the transfer section moves at a hand-over velocity substantially equal to the second transfer velocity in a hand-over area having a width; and the pickup velocity and the hand-over velocity are different from each other.
These configurations will be described with reference to the basic conceptual diagram of FIG. 1.
A transfer apparatus 1 provided between a preceding stage C1 and a subsequent stage C2 picks up a workpiece X to a transfer section 3 from the preceding stage C1, and hands over the workpiece X to the subsequent stage C2 after changing the transfer velocity of the workpiece X which has been picked up. Each of the preceding stage C1 and the subsequent stage C2 includes a drum, a conveyer, or any other transfer device, for moving the workpiece X at predetermined transfer velocities, and the configuration of each stage is not limited to any particular configuration.
The workpiece X has a predetermined length with respect to the transfer direction and a predetermined width. The predetermined length is a length that is less than or equal to the longitudinal dimension of the workpiece holding surface of the transfer section 3, and the predetermined width is a width that is less than or equal to the widthwise dimension of the holding surface. With the configuration illustrated in FIG. 1, the workpiece X is transferred in the longitudinal direction in the preceding stage C1, and then the direction thereof is changed in the transfer plane (the revolving plane of the transfer section 3) by means of a direction-changing section 5 provided in the transfer apparatus 1, after which the workpiece X is transferred in the widthwise direction in the subsequent stage C2. Note that the direction of the workpiece X may not be changed, or may be changed from the widthwise direction to the longitudinal direction.
As for the direction-changing section 5, the direction-changing section 5 may have a motor, for example, so that it is capable of turning the transfer section 3. However, in order to allow a rotating member 4 to rotate at a high velocity, it is preferred that the direction-changing section 5 is provided by using a direction-changing cam groove as will be described later. This is because it is then possible to reduce the weight of the rotating member 4. The direction-changing section 5 may alternatively be a rail such as a monorail instead of a direction-changing cam groove 48 as illustrated in FIG. 9. The driving force for turning the transfer section 3 may be supplied from a power source for rotating the rotating member 4.
The transfer apparatus 1 includes at least one transfer section 3 for picking up and holding the workpiece X. The transfer section 3 revolves around a rotation axis 11. In FIG. 1, the transfer section 3 (3a) immediately before picking up the workpiece X from the preceding stage C1 is shown in a solid line, and the transfer section 3 (3b) immediately after picking up the workpiece X is shown in a two-dot chain line. The transfer section 3 (3c) immediately before handing over the workpiece X to the subsequent stage C2 is shown in a solid line, and the transfer section 3 (3d) immediately after handing over the workpiece X is shown in a two-dot chain line.
The transfer section 3 picks up the workpiece X, which is supplied from the preceding stage C1 at a first transfer velocity (transfer velocity V1), in a pickup area adjoining the preceding stage C1 and having a width. At least in this pickup area, the transfer velocity of the transfer plane is maintained at a substantially constant pickup velocity V2. The transfer section 3 being located in the pickup area means that a predetermined point PL of the transfer section 3 is in the pickup area. In the example illustrated in FIG. 1, the predetermined point PL is located at the longitudinal center of the holding surface of the transfer section 3. The pickup velocity V2 is set to be substantially equal to the transfer velocity V1 of the preceding stage C1.
Herein, the pickup area is an area that is defined by an angle R1 about the rotation axis 11 in FIG. 1. The pickup area includes a pickup point SP at which the transfer section 3 comes closest to the preceding stage C1. Where the predetermined point PL is at the longitudinal center of the holding surface of the transfer section 3, it is preferred that the pickup area extends substantially by an angle R1/2 forward and backward with respect to the transfer direction about a line extending between the pickup point SP and the rotation axis 11. However, this may not be the case depending upon the workpiece X to be transferred and the configuration of the transfer section 3. The degree of the angel R1 depends upon the length of the workpiece X along the transfer direction in the vicinity of the pickup point SP.
As the transfer section 3 picks up the workpiece X in the pickup area, the transfer apparatus 1 changes via a velocity-changing section 2 the transfer velocity of the transfer section 3 from the pickup velocity V2 to a hand-over velocity V3. The velocity-changing section 2 is provided on the rotating member 4 rotating about the rotation axis 11, and is capable of reciprocating over a predetermined area of the rotating member 4. For example, the velocity-changing section 2 may have a motor so that it can move with respect to the rotating member 4. However, in order to allow the rotating member 4 to rotate at a high velocity, it is preferred that the velocity-changing section 2 is provided by using a velocity-changing guide that is provided on the rotating member 4 to be eccentric to the rotation axis 11, whereby the circumferential velocity of the transfer section 3 at the revolving surface thereof is changed, as will be described later. This is because it is then possible to reduce the weight of the rotating member 4. The velocity-changing guide may be a groove cam or a rail such as a monorail. Basically, such a velocity-changing guide has a generally circular shape or a generally elliptical shape eccentric to the rotation axis 11, and may include a straight portion and/or a curved portion. By using such a velocity-changing guide, the transfer section 3 can be moved substantially at a constant velocity for a period of time, as will be described later. The driving force for moving the velocity-changing section 2 along the velocity-changing guide may be supplied from a power source for rotating the rotating member 4.
The transfer section 3 releases the workpiece X in a hand-over area adjoining the subsequent stage C2 and having a width. The released workpiece X is handed over to the subsequent stage C2, and transferred at a second transfer velocity (transfer velocity V4). At least in this hand-over area, the transfer velocity of the transfer plane is maintained at a substantially constant hand-over velocity V3. The transfer section 3 being located in the hand-over area means that a predetermined point PS of the transfer section 3 is in the hand-over area. In the example illustrated in FIG. 1, the predetermined point PS is located at the widthwise center of the holding surface of the transfer section 3. The predetermined point PL and the predetermined point PS are different from each other because the transfer section 3 is turned. The hand-over velocity V3 is set to be substantially equal to the transfer velocity V4 of the subsequent stage C2.
The hand-over area is an area that is defined by an angle R2 about the rotation axis in FIG. 1. The hand-over area includes a hand-over point RP at which the transfer section 3 comes closest to the subsequent stage C2. Where the predetermined point PS is at the widthwise center of the holding surface of the transfer section 3, it is preferred that the hand-over area extends substantially by an angle R2/2 forward and backward with respect to the transfer direction about a line extending between the hand-over point RP and the rotation axis 11. However, this may not be the case depending upon the workpiece X to be transferred and the configuration of the transfer section 3. The degree of the angel R2 depends upon the length of the workpiece X along the transfer direction in the vicinity of the hand-over point RP.
As described above, one transfer method and one transfer apparatus of the present invention are configured so that the workpiece X is picked up by the transfer section 3 in a pickup area having a width at the pickup velocity V2 which is substantially equal to the transfer velocity V1 of the preceding stage C1, the transfer velocity of the transfer section 3 having picked up the workpiece X is changed to the hand-over velocity V3, and then the workpiece X is handed over to the subsequent stage C2 in a hand-over area having a width at the hand-over velocity V3 which is substantially equal to the transfer velocity V4 of the subsequent stageC2. Therefore, the transfer pitch of the workpiece X changes as the transfer velocity is changed.
Where the transfer velocity V4 of the subsequent stage C2 is higher than the transfer velocity V1 of the preceding stage C1, a transfer pitch P4 of the workpiece X, which has been handed over to the subsequent stage C2, is wider than a transfer pitch P1 in the preceding stage C1. Conversely, where the transfer velocity V4 of the subsequent stage C2 is lower than the transfer velocity V1 of the preceding stage C1, the transfer pitch P4 of the workpiece X, which has been handed over to the subsequent stage C2, is narrower than the transfer pitch P1 in the preceding stage C1. Then, as the predetermined point PS of the transfer section 3 moves away from the hand-over area, the velocity of the transfer section 3 changes from the hand-over velocity V3 to the pickup velocity V2 before the predetermined point PL of the transfer section 3 enters the pickup area.
In this way, the transfer velocity and the transfer pitch of the workpiece X are changed while the workpiece X is handed over from the preceding stage C1 to the subsequent stage C2, whereby the workpiece X can be efficiently transferred in a manner suitable for the process particulars, the process purposes, etc.
Moreover, a transfer apparatus of the present invention includes a vacuum adjustment section for attracting the workpiece X onto the transfer section 3 by way of vacuum suction at least while the transfer section 3 is in the pickup area, and stopping the vacuum suction so as to release the workpiece X from the transfer section 3 at least while the transfer section 3 is in the hand-over area. With this configuration, even when the workpiece X is by nature soft and unstable, the workpiece X can be smoothly handed over at a high speed without wrinkling the workpiece X.
Furthermore, in the transfer apparatus of the present invention, a holding surface of the transfer section 3 for holding the workpiece X is a convex surface so that the transfer section 3 can reliably pick up and hand over the workpiece X.
It is desirable that at the pickup point SP, the holding surface of the transfer section 3 approaches the workpiece X on the preceding stage C1 in a continuous manner in a direction from the front edge to the rear edge thereof along the transfer direction. For this purpose, the holding surface of the transfer section 3 is provided with an inclination such that the vicinity of the central portion thereof is raised, with respect to the front edge and the rear edge, along the normal line extending from the rotation axis 11 through the vicinity of the central portion of the transfer section 3. More specifically, it is preferred that the holding surface of the transfer section 3 coincides with the revolving plane of the transfer section 3 as the transfer section 3 at the pickup point SP is viewed from a direction along the extension of the rotation axis 11.
Similarly, it is desirable that at the hand-over point RP, the holding surface of the transfer section 3 moves the workpiece X held on the holding surface to continuously approach the transfer plane of the subsequent stage C2 in a direction from the front edge to the rear edge thereof along the transfer direction. For this purpose, the holding surface of the transfer section 3 is provided with an inclination such that the vicinity of the central portion thereof is raised, with respect to the front edge and the rear edge, along the normal line extending from the rotation axis 11 through the vicinity of the central portion of the transfer section 3. More specifically, it is preferred that the holding surface of the transfer section 3 coincides with the revolving plane of the transfer section 3 as the transfer section 3 at the hand-over point RP is viewed from a direction along the extension of the rotation axis 11.
Thus, it is preferred that the shape of the holding surface of the transfer section 3 satisfies the above-described two requirements at the pickup point SP and the hand-over point RP. However, it is not easy to actually produce a curved surface that satisfies such two requirements. Therefore, in the longitudinal direction, only the edges of the holding surface of the transfer section 3 may be formed each as a spherical surface with the normal line mentioned above being the radius thereof.
The holding surface may be formed by using a spherical surface with the normal line mentioned above being the radius thereof, a curved surface approximating to the spherical surface, a flat surface, or a surface made up of a combination thereof. In a case where the holding surface side of the transfer section 3 is made of an elastic material whose shape changes upon application of a pressure, the shape of the transfer section 3 may be any shape other than those described above.
The type of the workpiece X for use in the present invention may include, for example, a product or a semi-finished product of a sanitary napkin, a disposable diaper, disposable underpants, a bandage, other sanitary goods, and similar worn articles in general. Moreover, the form of the workpiece X may include a single sheet or a laminate of sheets layered on one another. The sheet may be liquid absorptive, liquid permeable, liquid semi-permeable, or liquid impermeable. Moreover, the sheet may be woven fabric or non-woven fabric. While the transfer method and the transfer apparatus of the present invention are particularly suitable for transferring the workpieces X of the types and forms as described above, the type and form of the workpieces X are not limited to those described above.